This invention is directed generally to power supply technology and more particularly to an ultra-wide input range power supply for circuit protection devices.
Power supply designs for small circuit and personnel protection/fault detection devices have operating constrains not common to most conventional line powered devices. More specifically, the supply must be designed such that 1) it operates under the extreme line voltage fluctuations typically seen during fault conditions, 2) efficiency is kept as high as possible to reduce the generation of excess heat, and 3) startup occurs fast enough to facilitate fault detection within the first line cycle after power is applied. The design discussed herein uses a novel combination of a linear and passive power converters to optimize the balance between efficiency, input voltage range, and fast start-up. A more detailed discussion of some of the problems solved follows:
Providing electronics with power throughout an extremely wide range of input voltage. A circuit performing fault detection in a circuit breaker must remain functional during the detection and tripping process. When a fault occurs, the input voltage to the power supply may fall to low levels. The power supply must continue, under those conditions, to supply the electronics with the energy required to detect the fault and open the circuit. Power supplies designed specifically for circuit breakers operate under the conditions present in load centers where large conductors provide AC power. However, as the need for xe2x80x9csmartxe2x80x9d detection of arcing and other types of faults expands to include protection at the outlet or load device, voltage drop under fault conditions increases due to the added series impedance of smaller wiring. The invention discussed herein features a wider input voltage operating range to meet these requirements.
Providing efficient power conversion. As the performance of xe2x80x9csmart circuit protectorsxe2x80x9d such as arc detection circuits increases, so does the power requirement. Space constraints and heat generated from the circuit breaker itself leave little allowance for added heat dissipation from the electronics. In particular, the power supply must be efficient enough to do the required power conversion without dissipating excess heat. Previous designs for lower power circuits use a linear or passive approach. Excessive power is lost in these designs when they are scaled for higher output power. The invention uses an efficient power conversion method that combines both linear and passive power converters to meet these requirements.
Providing power to the electronics very quickly after power is applied. To allow fault detection within the first line cycle of applied power, the supply must start up within a fraction of a 50/60 Hz line cycle (2.78 mS for ⅙ cycle at 60 Hz). The invention accomplishes this even at low line voltages.
The power supply shown in Square D""s U.S. Pat. No. 6,246,556 uses a passive power supply followed by a linear regulator (Ref FIG. 2 circuit block 60). In comparison, the invention discussed herein is an improvement on input voltage range, overall efficiency, and start-up time.
The invention is an improvement over previous designs that use single supply path. The improvement is an optimization of input voltage range, efficiency, and start-up time. Output regulation can be achieved over an extremely wide range of input voltages (10.1 or more) given properly selected components. Previous designs using a linear or passive approach have achieved a range of approximately 2:1. The extra wide range capability is made possible because the only constraints on input voltage are that 1) the peak input voltage does not exceed a value that would cause a violation of component ratings or power requirements, and 2) that the input voltage has an rms value that is a few volts above the regulated output voltage. Start-up time has also been improved over previous technologies by using the dual supply path approach.
Accordingly, it is a general object of the invention to provide an ultra-wide input range power supply for circuit protection devices.
Briefly, in accordance with the foregoing, a wide input range power supply for a circuit protection and/or fault detector device comprises a passive supply path comprising a passive supply for providing power to a load under nominal input voltage conditions at or near the nominal line voltage with minimum power loss, and a linear regulating supply path including a linear supply for supplying power to said load during start-up and at input line voltages below a first value and assisting in the passive supply at an input line voltage substantially below the nominal line voltage value.
In accordance with another aspect of the invention a method for supplying power over a wide range of input line voltages for a circuit protection device and/or fault detection device, comprises providing power to a load with minimum power loss using a passive supply path comprising a passive supply under nominal input voltage conditions at or near the nominal line voltage, providing power to said load at low input voltages below a first value using a linear regulating supply path including a linear supply, and assisting the passive supply using said linear regulating supply path at an input line voltage substantially below the nominal line voltage value and above said first value.
In accordance with another aspect of the invention a system for supplying power over a wide range of input line voltages for a circuit protection device and/or fault detection device, said method comprises passive supply means for providing power to a load with minimum power loss under nominal input voltage conditions at or near the nominal line voltage, and linear supply means for providing power to said load at low input voltages below a first value and for assisting the passive supply at an input line voltage substantially below the nominal line voltage value and above said first value.
In accordance with another aspect of the invention a linear/passive power converter, comprises a passive supply path comprising a passive supply for providing power to a load under nominal input voltage conditions at or near the nominal line voltage with minimum power loss, and a linear regulating supply path including a linear supply for supplying power to said load during strart-up and at input line voltages below a first value, and for assisting the passive supply at input line voltages substantially below the nominal line voltage value and above said first value.